In order to create various light effects and mood lighting in connection with concerts, live shows, TV shows, sport events or as a part on architectural installation light fixtures creating various effects are getting more and more used in the entertainment industry. Typically entertainment light fixtures creates a light beam having a beam width and a divergence and can for instance be wash/flood fixtures creating a relatively wide light beam with a uniform light distribution or it can be profile fixtures adapted to project image onto a target surface.
Light emitting diodes (LED) are, due to their relatively high efficiency and/or low energy consumption, long lifetime, and capability of electronic dimming, becoming more and more used in connection with lighting applications. LEDs are used in lighting applications for general illumination such as wash/flood lights illuminating a wide area or for generating wide light beams e.g. for the entertainment industry and/or architectural installations. For instance like in products such as MAC101™, MAC301™, MAC401™, Stagebar2™, Easypix™, Extube™, Tripix™, Exterior 400™ series provided by the applicant, Martin Professional a/s. Further LEDs are also being integrated into projecting systems where an image is created and projected towards a target surface. For instance like in the product MAC 350 Entrour™ provided by the applicant, Martin Professional a/s.
Different kinds of LEDs are currently commercially available. For instance LEDs may be provided as colored LEDs emitting light having a relatively narrow spectral bandwidth and thus emitting light of a single color. Typically LED based lighting products include a number of these LEDs of different colors and light generated by the LEDs are combined into an outgoing light beam. The intensity of each color can be adjusted relatively to each other whereby the color of the outgoing light beam can be varied as known in the art of additive color mixing. These lighting products can thus crate any color within the color gamut defined by the color of the LEDs. Typically this kind of lighting products includes red LEDs, green LEDs and blue LED and are known as RGB lighting products. The RGB lighting products can produce red, green and blue by turning the LED of only one color on while turning the remaining colors off. Further the RGB products can produce white light by turning all colors on (and approximately the same intensity) at the same time. However the color rendering index (CRI) of the white light is very low due the fact that the white is created by combining light with a narrow spectral bandwidth. The consequence is that an object illuminated by this white light, is not reproduced in its natural colors (as it appears when illuminated by sun light).
LEDs are also provided as white LEDs adapted to emit light having a broad spectral bandwidth and these may further be provided with different color temperature. These LED have a high CRI, as they emitted light over a large spectral bandwidth and are thus used in LED based lighting products to create bright white light, which can be used to illuminate objects and reproduce the objects in substantially in its natural color. However LED based lighting product based on white LEDs cannot create colored light beams without using a color filter as known in the art of subtractive color filtering.
RGBW LED based lighting products, where a number of single color LEDs and a number of white LEDs are combined, are also provided in order to be able to create different colors using additive color mixing and to improve the CRI of the white light. This is achieved by replacing a number of the colored LED with a number of the white LEDs. The white LEDs provide light having a broad spectral bandwidth and the CRI of the white light produced by such device is thus improved by white LEDs and the intensity of the white light is also increased. However the down side it that the intensity of the situated colors are reduced since there are fewer of these.
The LEDs are also provided in packages having a multiple amount a LED dies emitting light of different color and additionally also a led die emitting white light. The LED dies can be controlled individual, whereby the relative intensity of the light emitted by each die may be varied in relation to each other whereby the color of the outgoing light can be varied as known in the art of additive color mixing. Typically these LED packages includes a red die, green die, blue die and a white die and are known as RGBW 4in1 LEDs. The RGBW 4in1 LED are often used in RGBW LED based lighting products as described above.
In general it is desired to have a multi-colored LED lighting product with a high lumen and also a high CRI. However this is hard to achieve with the LED types describe above as it due to Etendue limitations is not possible to combine light from an unlimited amount of light sources into a light beam. The known LED based lighting products are as a consequence often designed for specific purposes and it is often necessary to have a large range of LED based lighting products in order to be able to provide a large variety of lighting solutions. This is especially the case in connection with projecting systems, where the light is coupled through an optical gate, where an image crating objects (GOBO) is positioned. An optical projecting system collect the light from the optical gate and is adapted to image the optical gate (and thus also the image crating object) a target surface. The light beam is very narrow when it passes the optical gate and such projecting systems are thus limited by Etendue. The Etendue, E=A*Ω, at the gate through which light is emitted has a limited opening area A and the imaging optics only collect light from a limited solid angle Ω. For light sources the Etendue can be calculated in the same way, where A is the radiating area, and Ω is the solid angle it radiates into.
It is desired to have very compact illumination devices which are difficult to achieve when more light sources are being integrated into the same illumination device. The space in light fixtures is often limited and it is difficult to fit many light sources into prior art fixtures, for instance because the optical components associated with the light sources often take up a lot of space. Another issue is the fact the light sources like LEDs generates heat which must be dissipated in order keep the LED running optimal. However it is difficult the remove the heat from the light sources in a compact illumination device, as the light sources are arranged in a small area wherefrom the head must be removed.
WO 2010/069327 discloses a moving head light fixture comprising a light generating head, where the head is carried in a yoke and rotatable to the yoke. The yoke is rotatable to a base. The head comprises at least one electronic circuit for LED control, where the moving head comprises a first cooling plate comprising a number of LEDs and a second cooling plate comprising the at least one electronic circuit for LED control. An air flow passage is running from at least one end of the moving head, through at least the first cooling plate and/or the second cooling plate and between the first cooling plate and the second cooling plate. The document discloses also to a cooling module for a moving head. This moving head provide an efficient cooling of the electronic circuits and the LEDs; however the moving head is relatively large and has a large cross sectional dimension.
US 2010/0238394 discloses a system for cooling an electronic display where an isolating structure may be used to allow ambient air to cool power modules. The isolating structure substantially prohibits containments which may be present within the ambient air from contacting sensitive electrical components on the power modules or otherwise. A gasket may be used to seal the interface between the power modules and the isolating structure. Heat sinks may be placed in thermal communication with the power supplies and fans may draw air through a narrow channel in which the heat sinks are located. In some embodiments the narrow channel may have the opposing surface of the channel defined by the rear portion of an LED assembly. Exemplary embodiments may use the ambient air to cool both the power modules and a closed loop of isolated gas within the electronic display.